As shown in FIG. 1, according to related art, a relay 14 is used to eliminate pop noise in a digital audio amplifier 10. In other words, the relay 14 is disposed between the digital audio amplifier 10 and a speaker 12, and a relay controller 16 senses a line voltage and operates the relay 14 when the digital audio amplifier 10 can operate normally. Then the relay 14 connects the digital audio amplifier 10 to the speaker 12, thus preventing the occurrence of pop noise in the digital audio amplifier 10.
The digital audio amplifier 10 includes a power PMOS transistor PM1, a power NMOS transistor NM1, a gate controller 101, and capacitors C1 and C2. An output-terminal filter, including an inductor L1 and a capacitor C3, is connected to an output terminal O.
However, the relay 14 is an electric mechanical device and bulk and expensive when compared with a general electronic device. Moreover, the relay 14 cannot be used independently and so requires the separate relay controller 16.